The objectives of the proposed research project are to gain more understanding of the biology of teratocarcinomas. We will use a new inbred strain (129/terSv) with a high susceptibility to teratocarcinogenesis in the testis to study the genetic basis for neoplastic potential of primordial germ cells. We will use a method of experimentally inducing testicular teratomas to study environmental influences on primordial germ cells which initiate their development into teratomas. We will define biologically factors which cause ovarian eggs in strain LT mice to develop into teratomas. We will study the chromosomes of strain LT parthenogenetic embryos, and investigate X-inactivation in cells without a paternal X.